how close is close enough?

[troypiggo]

Just curious about putting latitude and longitude into software or mount handset, and how accurate you need to do this.

What do you do? Put in degrees, minutes, and seconds, or just deg and min? I now have a GPS unit so imaging it'll be pretty precise, but before I had that I would just put in deg and min rounded off.

I had a look at Google Earth to see where my rounded off coords actually were, and it was 800m away from my real site. Is this enough to throw out any syncing/alignment/planetarium software?

[scarper]

I would say not noticably.

[allan gould]

Agree

[acropolite]

Troy as I understand it, within a few Km's is plenty accurate enough.

[Barrykgerdes]

I don't bother to change between Wiruna and Sydney. It does not stop a two star alignment and it is not noticeable in the computer programs.

Barry

[troypiggo]

Cool. Thanks for the feedback, guys.

[Dennis]

For stars, planets, DSO’s etc., a discrepancy of 800m is not really significant.

However, if you want to track the ISS and satellites then I think accurate GPS time and coordinates are required.

Cheers

Dennis

[darrellx]

Hi All

Just on this issue, if a location discrepancy can be upto say a kilometre or so and still be fine, what about actual time?

The reason I ask is that I have always sync'ed my laptop to an internet time service using a program Dimension4. I notice that with my GPS units, there is a difference of 90seconds between them and the internet.
Would 90 seconds make that much of a difference? I would have thought that it would, given the drift that can occur in that time.

Also, since the GPS navigation system runs on timed signals, I would expect that the GPS reported time would be more accurate and the one to work off. Is that correct?

Thanks
Darrell

[troypiggo]

Not sure, but reckon the GPS one would take preference. How do they both compare to http://www.timeanddate.com/worldclock/

[Dennis]

According to my Vixen Skysensor 2000 operator’s manual, for stars, planets, DSO’s etc., a discrepancy of a few minutes (of time) is not really significant in terms of GoTo accuracy. That is, for placing an object in the field of view of the eyepiece.

However, if you want to track the ISS and satellites then I think highly accurate GPS time and coordinates are required.

Cheers

Dennis

[darrellx]

Troy

It looks like http://www.timeanddate.com/worldclock/ is pretty close to GPS time.

Darrell

[mithrandir]

If you are going to use an internet time source, why don't you use an NTP client? There are several for Windoze, including the full blown ntp server. Your clock can be correct to within milliseconds. PC/laptop clock chips are not stable enough to maintain better accuracy. You can even feed the output of a GPS into the PC/laptop to manage the clock.

GPS time differs from UTC because UTC has leap seconds and GPS time does not. At present it is 15 secs ahead of UTC. The protocol tells your GPS the difference in seconds so it can display UTC compatible time.

I just tell ASCOM my mount has a GPS and let that worry about the time and location.

[Harpspitfire]

ive always wondered about this-- if you set your HC to the actual LMT instead of the wall clock time- you can actually be close to an hour off sky time, i know im 20 minutes off my time meridian- now i wonder if the HC adjusts for this or not?- i never did a comparison yet of initial go-to accuracy, has anyone ever did this?- john